As a long time space entusiats, I believe SPS can play and important role in the post oil peak economy. Developing the technology for SPS could also be the driving factor that keep the economy growing.

This reminds me of a bit from (I believe) Robocop 2 or 1 (paraphrasing):

"Thousands died this morning as a malfunction on the orbital peace platform laser accidentaly fired into a crowded neighborhood."

All these solar sattelite articles conveniently neglect the astronomical amount of energy it takes to put even 1 kg of material into geostationary orbit.

And if you mention that, then proponents suggest building vast factories on the moon to make all of this stuff. Yeah, THAT'S going to happen in time for peak oil problems.

It would be much wiser to invest our time & energy into conservation, flexible electric grids powered by wind & solar (where as the amount of power produced falls the price increases for consumers and big power drawing pieces of equipment power down accordingly) and crop-waste-to-ethanol production.

Japan plans SPS in longer term. With several hundred megawats of power. It's gonna be using microwaves (not laser), with intensity on Earth just a bit higher than that of cellular phones. Therefore, antena reciever has to be big, but you can still use space below antena (it allows about 1/2 of light to come through).
Plan suggest, that it should pay itself in similar time like nuclear plant.

And regarding heating of Earth - that's a minimal problem. We don't have global warming because of heat we produce by burning fossils/using any kind of energy, but because of CO2.

Licho wrote:Japan plans SPS in longer term. With several hundred megawats of power. It's gonna be using microwaves (not laser), with intensity on Earth just a bit higher than that of cellular phones. Therefore, antena reciever has to be big, but you can still use space below antena (it allows about 1/2 of light to come through). Plan suggest, that it should pay itself in similar time like nuclear plant.

And regarding heating of Earth - that's a minimal problem. We don't have global warming because of heat we produce by burning fossils/using any kind of energy, but because of CO2.

Just apply a little elementary physics and some modicum of commomsense.

1) Tell me how you are going to generate "several hundred megawatts" of microwave power. To generate 1 kW of CW microwave power (not pulsed) is already a challenge. I don't believe we have the technology for even a single MW.

2) Bearing in mind the inefficiency of CW TXs at those frequencies, I would imagine that, for a 500 MW space station, you would need about 4 to 6 km2 of solar panels to power it. How are you going to get them up there?

3) As such a station would need to be in geostationary orbit above the receiving dish, it will be in the dark for half the time.

4) How do you overcome atmospheric diffraction changes?

5) It is simple physics that if you increase the radiation energy into the earth's biosphere, so the latter will become warmer. However, half a dozen such stations would not make much difference.

6) What will you do with all the roast birds that will fall to earth (not to mention aircraft that inadvertently pass through the beam

7) How will you perform maintenance on a geostationary device using thermionic components?

Licho wrote:Plan suggest, that it should pay itself in similar time like nuclear plant.

But nuke plants CAN NOT afford the insurance, that is why in the US of A Congress limits their liability via the Anderson bill. So nuke plants do not 'pay for themselves'.

Licho wrote:And regarding heating of Earth - that's a minimal problem. We don't have global warming because of heat we produce by burning fossils/using any kind of energy, but because of CO2.

And that CO2 is still going to trap the additional heat load of this orbiting solar platform scheme. Every watt of eventual electrial power will become a part of a BTU of heat. That heat will be trapped by the already existing CO2 as you have noted.

Once every man made structure on this planet, wind machines are in use AND the energy needs are still unmet, then this obiting solar platform idea should be considered for implementation. Otherwise, it is nothing more than picking the pockets of citizens by the Governments for the benefit of global corporations.

Devil wrote:1) Tell me how you are going to generate "several hundred megawatts" of microwave power. To generate 1 kW of CW microwave power (not pulsed) is already a challenge. I don't believe we have the technology for even a single MW.

We don't need CW, plan calculates with normal 2450MHz transmitters similar to microwave owens There si probably going to be array of them on sattelite.The problem is, that you need large array of transmitters, to limit divergence of rays.

2) Bearing in mind the inefficiency of CW TXs at those frequencies, I would imagine that, for a 500 MW space station, you would need about 4 to 6 km2 of solar panels to power it. How are you going to get them up there?

Yes, one of the major problems. It calculets with modular design and many normal launches, but nothing undoable, just very costly. If we are going to build large ammount of such things, it's really much much cheaper (energy wise) to launch material from Moon, or build space elevator

3) As such a station would need to be in geostationary orbit above the receiving dish, it will be in the dark for half the time.

Erm, check the orbits It's not in shadow 1/2 of day, in fact it's in light 24/7 ! (Just rare do eclipses though happen).

4) How do you overcome atmospheric diffraction changes?

Diffraction affects MW minimally, and happens at relatively low altituted. Rectifier antena will be bigger than neccesary and probably of ellipse shape and will handle tiny changes.

5) It is simple physics that if you increase the radiation energy into the earth's biosphere, so the latter will become warmer. However, half a dozen such stations would not make much difference.

Yes, but just compare this energy to total solar energy we receive. Really, several GW change nothing..

6) What will you do with all the roast birds that will fall to earth (not to mention aircraft that inadvertently pass through the beam

Intensity near Earth is going to be just about 20-30mW per square cm (5mW can leak from MW owen by US standards), it won't kill anything. Birds can fly over it.

7) How will you perform maintenance on a geostationary device using thermionic components?

Biggest problem. Maintenance and servicing costs will be huge. SPS will receive constant damage from sun, space junk and micrometeorites..

The earth atomosphere absorbs about 40% of the solar energy on average; but the percentage really varies from place to place. Here in Arizona there is almost no humidity and clouds, I belive the percentage should be much smaller. And the SPS also have some transmission loss due to converting electicity to microwave, the microwave being absorbed by the atomosphere, and converting it back to electricity. If we can cover half of Ariona desert with solar panel, we can easily meet the electricity needs for entire US. It will be way cheaper than building it in space. Of course the key is to make cheap and efficient solar panel, and it is already in progress.

My local power supplier SRP already provides solar power generated electricity at the rate of 525 kW ( http://www.srpnet.com/environment/renewable.asp ). Hope they can expand this project. I do believe solar power is our savier and hold the key to our future. I am a senior engineer at a big semiconductor company and I'm looking into ways to make solar cells from defected wafers.

Would space based energy be useful if instead of sending it down to earth as pure energy instead you send down to earth finished products. heres my suggestion. You go capture an asteroid and use solar energy to mine and smelt the darn thing then send down to earth payloads of refined metals as slow meteorites.

Sun does not shine 24/7 on Earth and atmosphere absorbs significant ammount of energy. It's far more efficient to transmit it from space, even with relatively low efficiency conversion to MW and back. (Microwaves on this frequency loose only minimum energy in atmosphere). However, building costs for such thing are hug. Countries like Japan, don't have many excellent sites for ground solar farms, that's probably why they consider such extravagant plans. Some european scientists want to build solar plants over northern Africa, due to lack of suitable places in europe..

"The new communications satellites will orbit at an altitude of only a few hundred miles. Instead of hovering above a spot on the equator, low-orbiting satellites zip around the globe in as little as 90 minutes, tracing paths that oscillate about the equator, rising and dipping as many as 86 degrees of latitude. Because they are closer to the earth's surface, the solar collectors on the satellite can be a few hundred meters across rather than 10 kilometers. And because the microwave beams they generate would spread out much less than those from geosynchronous satellites, the ground rectennas could be correspondingly smaller and less expensive as well. By piggybacking onto these fleets of communications satellites--and taking advantage of their microwave transmitters and receivers, ground stations, and control systems--solar power technology can become economically viable."

Jack wrote:Neat idea---one would think that it would be an ideal way to generate power in isolated areas instead of using long transmission lines.

Sounds a hell of a lot like wind power, generate it away from the demand, and damn, how do you get the energy from where it is collected to where it is utilized..... umm.... an electric transmission line. Wait, they proclaim to solve one of the problems of wind, and use the same damned senario to argue for their pet project.

Also, from that article:

Scaling up to higher power levels would be straightforward, entailing simply the deployment of a larger amount of solar-collecting area in space. Power would be transmitted through the infrastructure of transmitters and receivers that will then be in place for the satellite communications systems. In this regard, microwave transmission has a decided advantage over conventional cable methods of transmitting power. A microwave system that is 80 percent efficient at sending 1 kilowatt will still be 80 percent efficient at sending 1 megawatt. This is fundamentally different from an electric utility transmission line, where you need thicker, and costlier, wires to carry more power. If too much power is put through a cable, it will melt the insulation.

This proposal is so full of holes it seems to me a distraction from addressing the issue of sustainable energy supply.

One such glaring hole is persuading the public that it's a good idea to have gigawatts of microwave energy being beamed at receivers on the planet from hundreds (thousands?) of satellites, any of which are liable to stray or get knocked off course, potentially irradiating God knows what population centres.

Another is the utterly prohibitive cost of public liability insurance against such an event.

A third is the predictably untenable money, energy & CO2 expenditure per unit of power supplied.

In the absence of global economic growth post peak I don't see who exactly is expected to bankroll such whimsy. In case anyone hadn't noticed, America is heading for bankruptcy. Broke. No credit-worthiness. Bust.

For me this sort of proposal is a further evidence that while one major chunk of the space industry is for military escalation, another is for distracting the population from the damage being inflicted on the only significant vessel we're ever going to have: namely the earth.

The propaganda appears to be: "Why give a damn - when we've wrecked this planet we'll go find another one !"